Patients who have a birth defect, a disfiguring disease, or who have suffered a burn or other traumatic injury often need reconstructive surgery. These patients have benefited in recent years from tissue engineering, an emerging field in which new tissue is grown in culture and manipulated so that it forms a desired shape. For example, a damaged cartilage meniscus in a patient's knee can be replaced with an artificially engineered meniscus. See, for example, Vacanti et al. (U.S. Pat. No. 5,041,138). Similarly, hollow spaces or lumens within tissues can be filled with cells suspended in, for example, gelatin, collagen, fibrin, or various hydrogels. See, for example, Griffith-Cima et al. (International Patent Application WO 94/25080).
Methods to regenerate skin, which reach beyond traditional skin grafting, have also been described. For example, keratinocytes have been used to generate an epithelial layer of skin (see, e.g., Hansbrough, J. Trauma, 30(12):S155-S162, 1992). However, cultured keratinocyte sheets lack a dermal component, and this is a potentially serious deficiency for achieving a successful replacement for full-thickness skin (Hansbrough, supra). Moreover, the “skin” generated by this and other presently available methods is not normally pigmented (because there are insufficient melanocytes) and it does not contain important structures such as hair follicles, sweat glands, sebaceous glands, and nail beds.